In recent years, mobile communication terminals are made to be thin, to have light-weight, and to achieve high performance of components, and have been evolved to smartphones that implement recording and reproduction of photos and videos, and functions such as music, navigation, games, and pen tablets, as well as a variety of additional communication functions such as value added communications using NFC (Near Field Communication), RFID (Radio Frequency Identification), Bluetooth, etc.
In order to perform various functions within a casing that is slim and compact as in a smartphone, it is also mandatory to make a main circuit board, an LCD (Liquid Crystal Display) or OLED (Organic Light-Emitting Diode Display) display panel, a touch panel, or digitizer panel made thinner.
In addition, in the case of recent mobile devices, display panels are enlarged to be 4 to 5 inches to 7 inches or 10 inches in size, and current consumption is increased based on the appearance of 3D (three-dimensional) games that require high-speed signal processing, LTE (Long Term Evolution) requiring high-speed graphics processing, and 4G (the Fourth Generation) mobile communications technology such as LTE-Advanced and Wibro-Evolution, and thus large-capacity batteries are adopted, thus generating a lot of heat from the batteries.
Lithium secondary batteries are mainly used as the large-capacity batteries used in the mobile terminals, and each of these lithium secondary batteries is configured to have a positive electrode, a negative electrode, and a separator, in which lithium cobalt oxide is used as a positive electrode anode active material, and graphite is used as a negative electrode active material. In the case of the lithium secondary batteries, the exothermic chemical reaction proceeds in a manner that lithium moves from the positive electrode to the negative electrode during charging, and moves back from the negative electrode to the positive electrode during discharging, thereby generating heat.
This secondary battery has a coupling structure where the secondary battery is inserted into a groove formed in the rear panel of a mobile terminal and then a rear cover is closed, or the secondary battery is coupled to a back surface of the rear cover.
When a large amount of heat is generated from the large-capacity battery, various electronic components on the main circuit board may cause malfunctions, and particularly a LCD display panel that is integrated with a touch panel may generate a greater amount of heat.
Accordingly, the mobile terminal equipped with the secondary battery uses an insulation sheet in order to block heat generated from the battery from being transferred into a main body of the mobile terminal.
Korean Patent Application Publication No. 10-2001-78953 discloses a heat radiation sheet in which heat generated from electronic circuits of a variety of electronic products, is timely absorbed and distributed by using a laminated heat radiation sheet without using a separate cooling fan, to thereby perform a heat radiation operation, and to thus ensure stability and reliability, implement lightweight and slimming, and enhance consumer satisfaction.
For this purpose, Korean Patent Application Publication No. 10-2001-78953 discloses a heat radiation sheet that is interposed between the upper surface of an integrated circuit having a heat generating function and a heat sink that is located on the just top of the integrated circuit so as to be direct surface-contact with the top of the integrated circuit, in order to disperse and radiate heat generated from the integrated circuit of the electronic product to the outside, in which the heat radiation sheet has a lamination structure of a thermally conductive aluminum foil coated with ceramic, a polyester film adhered to the aluminum foil with an adhesive, and a heat insulation polyurethane film that is integrated with the polyester film, and that provides an excellent touch function and an excellent thermal barrier effect.
In addition, Korean Patent Application Publication No. 10-2007-1760 discloses a heat insulation film having a size corresponding to that of a LCD device and that is disposed in front of the LCD device to prevent heat generated from a mobile terminal during a call for a long period of time from being delivered to a facepiece of the user through the LCD device, in which the heat insulation film is a film that allows transmittance of the visible light at maximum and blocks the passage of the heat and employs a low emissivity film that is generally used for construction purposes.
The Korean Patent Application Publication No. 10-2007-1760 also proposes a plan of inducing heat radiation at an air-cooling mode through formation of an air vent, but such a proposal is not applied at a very low frequency realistically, since an air flow is not smoothly distributed in electronic products at low efficiency.
As described above, the insulating films have been developed and used with a variety of structures for a variety of purposes, but are not being suggested as products that provide effective heat insulation functions so as to be used for the heat insulation films for the mobile terminals for minimizing effects on the mobile terminal display and the electronic components due to the heat generation from the internal battery in the mobile terminal that becomes lighter weight and slimmed depending upon adopting of the LCD or OLED display.
The insulation film for a mobile terminal is required to be formed of a thin film and to have a function of absorbing heat generated from a battery to minimize the heat that is transmitted to the main body of the mobile terminal.
However, the conventional insulating film has a film layer made of metal and consists of multiple layers, to thus cause the complicated manufacturing process and the high production cost.
It has been attempted to form the conventional insulating film having a relatively simple configuration by using a PET film or a nonwoven fabric or woven fabric. However, the PET film may have problems of causing a heat conduction phenomenon, or the nonwoven fabric or woven fabric may have problems of causing an easy heat transfer due to large pores.
To solve the above problems or defects, it is an object of the present invention to provide a heat insulation sheet and a method of manufacturing same, in which the heat insulation sheet is manufactured in a nanofiber web form by way of an electrospinning method, to thereby be made thin and have a plurality of fine pores, and to thus improve heat insulation performance.
In addition, it is another object of the present invention to provide a heat insulation sheet and a method of manufacturing same, in which the heat insulation sheet is manufactured by an electrospinning method to thus include a nanofiber web having a plurality of three-dimensional fine pores that are formed by a three-dimensional network structure of nanofibers, to thereby have an excellent function of capturing and accumulating heat.
In addition, it is another object of the invention to provide a heat insulation sheet and a method of manufacturing same, in which inorganic particles are contained in a spinning solution, to thereby provide the insulation sheet having an excellent heat resistant function.
The technical problems to be solved in the present invention are not limited to the above-mentioned technical problems, and the other technical problems that are not mentioned in the present invention may be apparently understood by one of ordinary skill in the art in the technical field to which the present invention belongs.